Recently, copper having a resistance lower than that of aluminum has become more frequently employed as a wiring material, and a wiring formation technique called Damascene method has been studied as a technique for forming wirings by processing above mentioned copper. This Damascene method is roughly classified into Single-Damascene and Dual-Damascene.
Single-Damascene is a method in which, for example after a wiring groove is formed in an insulating film, a copper film for forming a wiring is deposited on the insulating film and in the wiring groove, and then, the copper film is polished by means of, for example, Chemical Mechanical Polishing (CMP) such that the copper film remains only in the wiring groove, thereby forming a buried wiring in the wiring groove.
Dual-Damascene is a method in which, after a wiring groove and a connection hole, which is for providing connection with a wiring of the lower layer, are formed in an insulating film, a copper film for forming a wiring is deposited on the insulating film, and in the wiring groove and the connection hole, and then, the deposited copper film is polished by means of CMP such that the copper film remains only in the wiring groove and the connection hole, thereby forming a buried wiring in the wiring groove and the connection hole.
In a copper wiring which is formed in the above described manner, the copper atoms constituting the copper wiring diffuses into an interlayer dielectric film, which is problematic. The diffusion of copper atoms to the interlayer dielectric film occurs when the copper atoms are ionized since they are in contact with the interlayer dielectric film, and the ions blends into the interlayer dielectric film. When copper atoms are diffused into the interlayer dielectric film in above described manner, insulation resistance of the interlayer dielectric film is deteriorated, thereby resulting in deterioration of reliability between wirings. Therefore, in order to prevent the copper atoms from diffusing into the interlayer dielectric film, a barrier conductive film which is, for example, tantalum, titanium, or tungsten based, is formed between the copper wiring and the interlayer dielectric film (e.g., see Japanese Patent Application Laid-Open Publication No. 2003-297832 (pages 7 to 9)).
Meanwhile, although silicon oxide based insulating films have been used as interlayer dielectric films, recently, in order to reduce signal delay in a high-density wiring, organic insulating films which can reduce wiring capacitance with a dielectric constant lower than that of silicon oxide films and can bring about PFC (PerFluoro-Compound) reduction effects, have been studied for use as interlayer dielectric films.